The present invention relates to closures and in particular to a zipper closure for post applied application to a filled package.
Reclosable plastic bags, that is, bags provided with a pair of mating profiles that form a zipper to render the bags readily reclosable after initial opening are becoming increasingly popular as primary packaging for a range of products, particularly food products. Such packaging and the methods of making the same are described, for example, in U.S. Pat. No. 4,709,533 and the patents discussed therein.
It will be appreciated that the primary concern in the manufacture of food packaging is to ensure that the package maintains the necessary barrier properties and integrity to protect the food contained therein. With certain foods, such as potato chips or popcorn, the packaging must further be "pillowed" to provide a degree of shock protection for the contents. Accordingly, when it is desired to package such foods in zippered packaging, care has to be taken to ensure that the film from which the package is formed possesses the necessary properties to protect the food to be packaged therein and that application of the zipper to the film does not interfere with the integrity of the final package or alter the nature of the final package. It should be understood that the zipper provides only a secondary closure for the package that enables the contents of the package to be effectively retained and removed after the primary seal of the package has been ruptured.
High volume food and other similar products are usually packaged on form, fill and seal equipment in which the package is formed and filled, often in-line with the food production equipment. After filling the package must be hermetically or otherwise sealed to protect the contents. When such products are to be packaged in zippered packaging, the zipper is either preapplied to the film from which the package is formed or applied to the film at the form fill and seal equipment. This has previously required a modification of such form, fill and seal equipment to accommodate the zipper and/or resulted in a slow down in the filling speed of the equipment, which in turn has caused reluctance on the part of some manufacturers to change from conventional packaging to zippered packaging.